1. Field of the Invention
This invention relates to an image forming apparatus which is capable of interchanging an engine, a sheet feed system, or a discharge system of the image forming apparatus.
2. Description of the Related Art
For an image forming apparatus such as a copying machine or a printer, there has been generally known image forming apparatuses that are capable of selectively making only a monochrome copy or both of the monochrome copy and a color copy depending on a user's demand.
There exists an image forming system having a structure in which a main body of the above-mentioned image forming apparatus is connected to another device to provide a function that matches an intended purpose in cooperation between the image forming apparatus and another device, which cannot be realized solely by the image forming apparatus.
JP-A-H11-292335 A discloses a copying machine having a structure in which an image reading device is connected to an image forming apparatus to copy a document image that has been read by the image reading device. Also, there has been proposed an image forming apparatus in which plural sheet feed units that also function as a base of the image forming apparatus are interchangeably stacked, which enables various device configurations of sheet feed devices and the like. In addition, there has been known an image forming apparatus that is connectable to a post-processing device (accessory) that sorts or staples for sorting recording sheets which have been printed by the image forming apparatus.
On the other hand, there have been proposed various image forming apparatuses having a structure in which a unit can be incorporated in the apparatus. For example, for an image forming apparatus of the standard specification which suppresses the functions of the apparatus main body to the minimum, there has also been proposed a device configuration in which a duplex transport unit reverses a recording sheet that has been printed in order to newly perform duplex printing can be incorporated into the image forming apparatus. There has been known the image forming apparatus in which part of units within the apparatus are detachably attached to the apparatus as described above, thereby matching the intended purpose of the user.
Up to now, the user selects an image forming apparatus that realizes a desired function or performance (monochrome, color, the number of sheets outputted per minute, or the like), or the usability (size or discharge position) from diverse lineups. In addition, in the case where the user demands a function or performance (duplex, sort, or stable) which cannot be obtained solely by the selected image forming apparatus, the user selects the device configuration in such a manner that the image formation apparatus is combined with the above-mentioned incorporatable accessories, diverse devices, or diverse units so as to utilize the desired function or performance. Then, the image forming apparatus operates in cooperation with the connected accessories, diverse devices, or diverse units, thereby making it possible to conduct a diversity of operation. As a result, various conveniences are supplied to the user.
However, in the conventional image forming apparatus, device designing is performed while simulating the merchantability of the device configuration or the accessory configuration so that a large majority of users are capable of using the device in an optimum state. As a result, the device configuration does not flexibly meet the wishes of the individual users.
That is, because the conventional image forming apparatus is so configured as to conduct the system operation in cooperation with the accessories, the diverse devices, or the diverse units, the conventional image forming apparatus conducts nothing other than the operation depending on the operation mode, the function, or the performance which can be conducted in the above-mentioned structure. Therefore, for example, in the case where the sheet feed unit or the accessory is connected to the image forming apparatus, the operation performance of the entire device may be limited depending on the combination of the performance and the function of the image forming apparatus. Also, the operation performance of the entire image forming apparatus is also decided according to the configuration of an image forming unit, a sheet feed unit, or a sheet transport unit within the image forming apparatus. As a result, there is a case in which the image forming apparatus cannot sufficiently meet the functions that are demanded by the individual users.